1. Field of the Invention
The present invention relates to bicycle rims and other like rims that are composites manufactured as multiple components that are assembled after molding.
2. Prior Art
While current light-weight bicycle rim technology encompasses composite rim and wheel construction, most such composite rims are manufactured as a one piece component with no secondary assembly required to complete the rim structure. Where a composite rim has been manufactured as multiple components and assembled after molding, the segmentation of the rim is through the center-line of the xe2x80x9cZxe2x80x9d axis as opposed to the xe2x80x9cXxe2x80x9d or xe2x80x9cYxe2x80x9d axis, and such sections have often not been well matched creating a finished rim that is warped or is out of round. Additionally, in practice, current composite rim construction has been based upon a woven reinforcement design and no product is currently available that is marketed as a unidirectional laminate structure.
Further, because high pressure is required to sufficiently compact the multiple unidirectional layers, also known as xe2x80x9cplysxe2x80x9d of unidirectional fibers of the rim structure, a heavy solid shaped mandrel is required to allow for a creation of a pressure thereagainst that is necessary to compact such-multiple layers. The present invention that utilizes a two piece rim that are joined by bonding at their ends, with each rim piece or half section formed on a mandrel capable of expanding under curing heated to create an outwardly directed force on the material laid up on the mandrel surface, compresssing layers against a mold cavity wall. Such a heavy internal pressure creating mandrel is extracted after curing, leaving only the hollow, light-weight rim half section . The molding technique of the invention further deviates from traditional composite molding techniques, such as are used with fiberglass, or carbon fiber, molding techniques due to the high pressure as is required to compact the multi-ply laminate. Where traditional molding techniques required only a maximum of fourteen (14) psi to appropriately mold the laminate, the invention requires a minimum of two hundred fifty (250) psi to sufficiently compact the multiple layers or plys forming the rim of the invention.
A bicycle rim, or like rim, is constructed from layers of plys of unidirectional fiber layers to provide a rim that improves upon traditional metal of other composite construction by a decrease in weight, an increased strength and stiffness while providing a profile having low aerodynamic drag characteristics. These rim improvements decrease the time and/or effort required by a cyclist to pedal a given distance, providing for an improvement in acceleration and a decrease in required human power output. This increased efficiency and performance is achieved by a decrease in rim rotational inertia and by a creation of an aerodynamically enhanced shape. The light weight construction and aerodynamically enhanced shaped is achieved through a unique combination of a use of multiple layers of unidirectional reinforcement that is applied at high pressure in a unique molding technique where the rim is formed in two identical hollow hemispherical sections that are joined together at their ends using internal inserts telescoped into the rim section ends ends that are pushed together and bonded therein, and by fitting a V-shaped external gusset over the joined ends, with the internal insets and external gussets each receiving a bonding material, such as a standard two part epoxy structural adhesive, applied thereto prior to fitting the components together, creating a continuous structure.
It is an object of the present invention is to provide a fiber reinforced rim that is exceptionally strong and light in weight by a manufacture of separate hollow hemispherical rim sections by an application of layers or plys of unidirectional fibers that are arranged at distinctive crossing angles and within separate planes, that are subjected to heat and high pressure to create identical rim sections for joining at their ends by an adhesive bonding into a rim that is appropriate to carry design static and dynamic loads.
Another object of the present invention is to provide a rim to carry anticipated static and dynamic loads by formation of a reinforcement by an application onto a mandrel of multiple plys of unidirection fibers that are arranged in distinctive crossing angles, and within separate planes, onto a removable mandrel and including applications of an epoxy thermoset resin or a nylon thermoplastic resin to the layers of fiber, and maintaining the mandrel and reinforcement at a temperature of approximately two hundred five (205) degrees Celsius for a period of time to cure the reinforcement to form the rim hemispherical sections that are matched, and the matched rim half sections are joined at their ends into a circular rim.
Still another object of the present invention is to provide, as separately manufactured items, identical hollow hemospherical rim sections and joining a pair of matched rim sections by telescoping the rim sections ends together over each of a pair of internal insert coated with an adhesive and by bonding a V-shaped gusset over each of the butting ends joint.